Ibid.: what it means and how to use it
“Ibid.” (from Latin ibidem, “in the same place”) tells the reader a footnote points to the same source as the note right above it. Step through a paragraph to see exactly when that works.
Sleep debt builds across a school week1,
- Maya Nguyen, Sleep and the Student Brain (Chicago: University of Chicago Press, 2021), 14.
Note 1: First time you cite Nguyen: a full note with every detail.
The two rules of ibid.
- Only for the immediately preceding note. If any other source appears in between, ibid. would point to the wrong work.
- Add the page if it changed: “Ibid., 17.” Leave it off if it’s the same page.
Ibid. can also never be the first note on a new page in some house styles, because the reader can’t see the note it refers to. Shortened notes avoid that problem, which is one reason the Chicago Manual of Style’s 18th edition moved away from ibid.
Ibid. vs op. cit. vs a shortened note
| Form | Meaning | Use today |
|---|---|---|
| Ibid. | Same source as the previous note | Allowed in Chicago, common in law (OSCOLA) |
| Op. cit. | “In the work cited” earlier | Obsolete in Chicago; avoid |
| Nguyen, Sleep, 17. | Shortened note | Chicago 18’s preferred form |
Build full and shortened notes with the Chicago footnote generator.
Questions students ask
What does ibid. mean?
Ibid. is short for the Latin “ibidem”, meaning “in the same place”. In a footnote, it means the source is the same as in the note immediately before.
How do you use ibid. with a page number?
If the page is different, add it: “Ibid., 17.” If the page is the same as the previous note, write just “Ibid.”
Can I use ibid. in APA or MLA?
No. Ibid. belongs to footnote systems such as Chicago notes-bibliography, OSCOLA (law) and some Harvard variants. APA and MLA use parenthetical citations instead.
Is ibid. still used in Chicago style?
The Chicago Manual of Style, 18th edition (2024), discourages ibid. and recommends shortened notes instead, but it has not banned it. Follow your instructor’s preference.
Is ibid. italicised?
Not in Chicago style; write “Ibid.” in roman type with a capital I at the start of a note. Some older guides italicise it.